Long term evolution (LTE) carrier aggregation allows user equipment (UE) to receive and send data over more than one carrier if additional or secondary carriers are configured and activated for a carrier aggregation capable UE. Adding a secondary carrier to a UE is equivalent to adding a secondary cell. Secondary cells can be dynamically activated or deactivated by an evolved node B (eNB) base station. The secondary cell configuration information is communicated to a UE through radio resource control reconfiguration messages transmitted via the UE's primary cell. Once a secondary cell has been configured, the eNB sends media access control (MAC) control elements (MAC CEs) to the primary cell advising the UE whether the secondary cells are activated or deactivated. When, the downlink secondary cells are activated, the UE monitors the physical control channel (PDCCH) for the secondary cell and provides downlink channel condition reports to the eNB.
Activated secondary cells potentially increase throughput for UE data transmission. However, the UE consumes more battery power while monitoring the PDCCH for the activated secondary cells. Also, activated secondary cells demand greater memory resources and processing power at the eNB. Therefore it is preferable that carrier aggregation is only provided to a UE when there is a benefit, such as increased throughput. Third generation partnership project (3GPP) standards provide communication interfaces between the eNB and the UE but do not define an algorithm for making effective use of carrier aggregation, while taking into consideration battery savings in the UE and processing load and available memory in the eNB.